Identification of Small-Molecule Bioactive Constituents from the Leaves of Vaccinium bracteatum Confirms It as a Potential Functional Food with Health Benefits

Abstract

The health benefits of Vaccinium bracteatum are well recorded in ancient Chinese medical books and were also demonstrated by modern researches. However, the relationship between its beneficial functions and specific chemical constituents has not been fully characterized. This study investigated the bioactive small-molecule constituents in the leaves of V. bracteatum, which afforded 32 compounds including ten new ones (1–9) and ten pairs of enantiomers (9–18). Their structures with absolute configurations were elucidated by spectroscopic methods, especially nuclear magnetic resonance (NMR) and electronic circular dichroism (ECD) analyses, with 1–4 bearing a novel revolving-door shaped scaffold. While half-compounds exhibited decent antioxidant activity by scavenging 2,2-diphenyl-1-picrylhydrazyl (DPPH) radicals, all except 19 and 20 exerted significant capturing activity against diammonium 2,2’-azino-bis(3-ethylbenzothiazoline-6-sulfonate) (ABTS) radicals. In addition, the new iridoids 1, 5, 6, and 7 exerted apparent neuroprotective activity toward PC12 cells, with 1 being comparable to the positive control, and selective compounds also displayed anti-diabetic and anti-inflammatory properties by inhibiting α-glucosidase and NO production, respectively. The current work revealed that the bioactive small-molecule constituents could be closely related to the functional food property of the title species.

Anti‐inflammatory Polyketides from an Endophytic Fungus Chaetomium sp. UJN‐EF006 of Vaccinium bracteatum

“…The absolute configurations of compounds 1-7 were determined by time-dependent density functional theory (TD-DFT) based electronic circular dichroism calculations with Gaussian 09 software at the B3LYP/6-311G (d,p) level in vacuo. [12,21]…”

“…[7] As part of our recent years' efforts to search for bioactive ingredients from medicinal herbs with dietary values, [8][9][10][11] we have lately isolated iridoids and lignans with diverse bioactivities as the major chemical constituents in the leaves of Vaccinium bracteatum. [12] Since plant-derived endophytic fungi have emerged as an important source of bioactive natural products in the last two decades, [13][14] the chemical diversity of V. bracteatum metabolites has thus inspired us to start a project aiming to explore the bioactive metabolites produced by the endophytic fungi of this plant. Therefore, a Chaetomium sp.…”